Flipping polarity or time-shifting one mic in a multimiked recording is a free tonal adjustment

When multiple microphones capture the same instrument (multimiked sources), their phase and polarity relationships determine the combined timbre. At the balancing stage: (1) check polarity — the mics may have been set up with opposite polarity, causing comb filtering; correcting this fills out the combined sound; (2) time-shift one mic against the others to test for improved phase alignment using the ‘phase-reverse and maximize cancellation’ technique; (3) at lower blend levels, deliberately introducing polarity inversion or short delays creates tonal variations that would take all day with EQ, with zero DSP processing artifacts. The technique is completely free of side effects.

Examples

Overhead mics above a drum kit: flip polarity of one side and time-shift to find maximum cancellation of the snare hit, then re-flip to normal polarity — the snare will be more centered and solid in the mix.

Assessment

You have a snare drum recorded with a top mic and a bottom mic. The bottom mic’s waveform is inverted. What happens if you leave the polarity uncorrected? How do you perform the time-shift phase-matching procedure?